Canine detection of radio-telemetered brown treesnakes

We are investigating canine teams (dogs and their handlers) on Guam as a potential tool for finding brown treesnakes (BTS) (Boiga iregularis), especially incipient populations on other islands. Canine teams have demonstrated proficiency at finding captive snakes in hidden tubes. Teams also find free-ranging BTS in various habitats, but detection rates for the latter are unknown. Dog handlers usually rely on visual searchers to locate BTS once a dog has signalled snake presence. At times, dogs signal but the visual search team cannot locate the snake; this complicates attempts to quantify detection rates. Our research aimed to estimate detection rate of free-ranging BTS by canine teams as a function of snake attributes, characteristics of snake refugia, and environmental conditions. Canine teams searched a defined 40m × 40m forested area with a snake that had consumed a dead mouse containing a radio-transmitter. Trials were conducted during the morning, when snakes were usually hidden in refugia. A tracker knew the snake’s location, but dog handlers and data recorders did not. We recorded data on dog alerts and on-scent behaviour during trials. Out of 86 trials, the two canine teams had an average success rate of 36%. This study provides initial estimates of canine team efficacy when searching in complex habitats in information on optimizing visual search strategy after dog signals snake presence (defining size of area to search, identifying preferred refugia, etc.). We discuss experimental design, challenges and initial results.